Method for preparing aromatic acyl fluorides



Patented Aug. 8, 1950 PATENT ori ice 1 I; "an Pont-de Nemours & Company, Wilmington, Deli-, -a -corporation of Delaware 'Ifhis inyentior i" relates" to improvernents infthe preparation of acyl iluc arides and-- more particularlyto a proce for t e preparation of arematic'acylfluorides.

The known methods for preparing aromatic acyl fluorides involve indirect complicated pro cedures. For example," benz'oyl fluoride has been prepared. in thepas't bylfirst-making the acid chloride andthen converting" this to the fluoride by reaction with'potassium 'hydrog en"fiuoride'. such' methods are'not feasible for use in the preparation of highly -substituted aromatic acyl fluorides'fThere isthus a need for; a direct method for preparing aromatic acyl-{fluorides from readily available materials.

contacting an'aryldiazoniurn fiuoborate withcar looninonoxide'under"anhydrousfconditions.

I In 'oneembodiment of'thisinvention the aryl- 'diaz'on'iii'rn fluoborate is heated at 60to=125 C. in'a-nfin'ert solvent, e. g.,'an alcohol or a hydrocarbon," with carbon monoxidefunder s'uperat mospheric pressured g. 209-19001 atr'n'." Reac tion times of from i-to'f8 hours' or more aresuit-i able under these conditions. The resulting aromatic 'acyl fluoride can be isolated 'f romfthe"re action, mixture, by,conventiona1 means, egg by fractional distillation of the filtered reaction mixture.

In another embodiment of this invention, the

'carb'on monoxide used is generated in situfrom a metal carbonyl. In this case the aryldiazonium fluoborate is added gradually to an excess, e. g., 10 to- 50% excess, of a metalcarbonyl such as nickel-carbonyl in the presence of-an inert'polar ide and, gaseous reaction products;

mixture is removed from the reactor. and'filtered,

Application December 24, 1948, S erial No. 67,251

9-Claims. J (Cl. 260-544) vide a gradual reaction and to control the rate of generation of by-product gaseous, materials. The reaction is substantially completed" byi 'the time all "the aryldiazonium fluob'orate' has b' e en added tothe' reaction mixture. The resulting aromatic acyl'fiuoride is isolatedbyfractional distillation of :thefiltered reaction mixture.

The aryldiazon'ium' fiuoborates used'as startingmaterials in..the"process of thisinvention can be prepared from the corresponding 'aryl amines by diazotization of the amine "hydro chloride followed by reaction of the ary-ldiazonium' chloride with fiuoboricacid'. "Thepreparation of benzenediazonium fiuoborate by this procedure-isdesc'ribed in detail by D. T. Flood in Organic Syntheses 13, 46 (1933). W

The invention is illustrated'in further detail by the following examples in which the proportions of the reactants are"expressed'in'partsby' weight unless'otherwise noted. v

the addition. i- The reaction mixture; after the addition of thei benzenediazoniur'n fiuoborate is completed, is filtered to remove nickel chloride and the solvent removed from'th'e -filtrate under reduced pressure. The" residue is fractionally distilled, and there is obtained '13 parts, corre; sponding to a32% yield, "of benzoyl fiuoride, E.P."5'6 C. at 1.5mm.

I Fifty-parts" of .benzenedi'azonium fluoborate'and 200 DSJItSaiOf absolute ethanol'are charged "into a pressure reactor, the reactoris 'closed', carbon monoxide introducediu'nder 1000 atm. "pressure;

and the reactor heated at C. for 56 hours. After cooling to room temperature, the reaction vesselis vented to remove excesscarbon monox- The reaction the solventcis removed from the filtrate under reduced pressure, and the residue is fractionally distilled. There is obtained 14.5 parts, 43% of theory, of benzoyl fluoride boiling at 64 C. at

4 min. The benzoyl fluoride is identified by hydrolysis to 'benzoic acid.

The preparation of aromatic acyl fluorides by the process of this invention has been illustrated with particular reference to the reaction of benzenediazp ium fluobcrate with carbon monoxide; however, et er aromatic diazonium fluoborates can be converted to the aromatic acyl fluorides in a similar manner. For example, the use of p-nitrobenzenediazonium fluoborate gives pnitrobenzoyl fluoride, p-toluenediazonium fluoborate gives p-methylbenzoyl fluoride, o-chlorobenzenediazonium fluoborate gives o-chlorobenzoyl fluoride, and betariaphthalenediazonium fluoborate gives beta-naphthoyl fluoride. The substituted aryldiazonium fluoborates are readily obtainable from the corresponding substituted aromatic amines, hence the process of this inven-' tion is well adapted to the preparation of the corresponding substituted aromatic acyl fluorides as Well as the unsubstituted aroyl fluorides, such asbenzoyl fiucride.

As indicated by the examples, the carbon monoxide employed in the process. of this invention can be supplied as gaseous carbon monoxide under the desired pressure, or it can be generated in situ in the reaction mixture from a metal carbonyl, In addition to the nickel carbonyl of Example I, carbonyls of other metals of Group VIII, Series 4, of the Periodic Table, e. g., cobalt carbonyl, can also be used. The metal carbonyls are preferably used in a slight excess, e. g., -50% excess, over the amount stoichiometrically equivalent to the aryldiazonium fluoborate used.

The reaction of aryldiazonium fluoborates with carbon monoxide in gaseous form. is conveniently carried out in the presence of an inert solvent. Suitable solvents include hydrocarbons, e. g., benzlene and saturated aliphatic hydrocarbons; a1 cohols, e. 'g., methanol and ethanol; and ethers, such as diethyl ether, dibutyl ether, tetrahydrofuran, and dioxane. On the other hand, when the source of the carbon monoxide is a metal carbonyl it is preferable, to use a. polar solvent. In this case suitable solvents, include alcohols, such as methanol and ethanol.

The aromatic acyl fluorides obtained. by the process of this invention are useful as. chemical intermediates; and' are especially useful for the preparation of the corresponding aromatic carboxylic acids.

AS; indicated previously, the process of this inavention has the advantage over the hitherto known methods for making aromatic acyl fluorides; of providing a direct method for preparing such acyl fluorides. It, is, especially valuable. for the reaction of aryldiazonium fluoborates, having substituents of various types on the aromatic ring since the substituted aryldiazonium. fluoborates can readily be prepared from the corresponding substituted aromatic amino or nitro compounds.

As many apparently widely. different embodiments of this invention may be made without departing from the spirit and scope thereof. it is tobe understood that this invention is not limited to the specific embodiments thereof except as defined in the appended claims.

I' claim:

1. A method for preparing an aromatic acyl fluoride which comprises reacting under anhydrous conditions in an inert solvent an aromatic diazonium fiuoborate with carbon monoxide-at a temperature within the range of ordinary temperature to C. and under a pressure within the range of atmospheric to 1000 atmospheres.

2. A method for preparing an aromatic acyl fluoride which comprises reacting under anhydrous conditions in an inert solvent an aromatic diazonium fiuoborate with carbon monoxide at a temperature of 60 to 125 C. and under superatmospheric pressure of 200 to 1000 atmospheres.

3. A method for preparing an aroyl fluoride which comprises reacting under anhydrous conditions in an inert solvent an aryldiazonium fluoborate with carbon monoxide at a temperature within the range of ordinary temperature to 125 C. and under a pressure of 200 to 1000 atmospheres.

4. A method for preparing an aroyl fluoride which comprises reacting under anhydrous conditions in an inert solvent an aryldiazonium fluoborate with carbon monoxide at a temperature of 60 to 125 C. and under superatmospheric pressure of 200 to 1000 atmospheres.

5. A method for preparing benzoyl fluoride which comprises reacting under anhydrous conditions in an inert solvent benzenediazonium fluoborate with carbon monoxide at a temperature within the range of ordinary temperature to 125 C. and under a pressure within the. range of atmospheric to 1000 atmospheres.

6. A method for preparing benzoyl fluoride which comprises reacting under anhydrous conditions in an inert alcohol solvent benzenediazonium 'fluoborate with carbon monoxide at a. temperature of 60 to 125 C. under superatmospheric pressure of 200 to 1000 atmospheres.

7. A method for preparing an aromatic acyl fluoride which comprises reacting; under anhydrous conditions, in an inert polar solvent an arcmatic diazonium fluoborate with carbon monoxide formed in situ from a metal carbonyl and an anhydrous acid ata temperature within the range of ordinary temperature to 125 C. and under a pressure within the range of atmospheric to 1000 atmospheres. I

8. A, method for preparing an aroyl fluoride which comprises, reacting under anhydrous conditions in an inertpolar, solvent an-aryldiazonium fluorborate with carbon monoxide formed in situ from nickel carbonyl and an anhydrous acid at a'temperaturewithin the range of ordinary temperature to 125 C. and: under a pressure Within the range of atmosphericto. 1000 atmospheres.

9. A method for preparing benzoyl fluoride which comprises reacting under anhydrous conditions in an. inert alcohol solvent 'benzenediazonium fluoborate with carbon monoxide formed in situ from, nickel carbonyl and anhydrous hydrochloricacid at a temperature within the range of ordinary temperature to 125 C. and under a pressure within. the range of atmospheric to 1000 atn'ic' s);$heres.v V a A ROBERT G. LINVILLE.

REFERENCES CITED Theiollowing references are of record in the file-of this patent:

Number 

1. A METHOD FOR PREPARING AN AROMATIC ACYL FLUORIDE WHICH COMPRISES REACTING UNDER ANHYDROUS CONDITIONS IN AN INERT SOLVENT AN AROMATIC DIAZONIUM FLUOBORATE WITH CARBON MONOXIDE AT A TEMPERATURE WITHIN THE RANGE OF ORDINARY TEMPERATURE TO 125*C. AND UNDER A PRESSURE WITHIN THE RANGE OF ATMOSPHERIC TO 1000 ATMOSPHERES. 